docs: def has_successor(self, graph, orig, dest, branch, turn, tick, *, forward=None):
          """Return whether an edge connects the origin to the destination at the given time.
  
          Doesn't require the edge's index, which makes it slower than retrieving a
          particular edge.
  
          """
          if forward is None:
              forward = self.db._forward
          return dest in self._get_destcache(graph, orig, branch, turn, tick, forward=forward)